1. Field of the Invention
This invention relates to a method and device for assembling a fuel cell stack. More particularly, the present invention relates to a method and device for assembling a fuel cell stack comprising a large number of fuel cells.
2. Description of the Prior Art
A fuel cell stack in a fuel cell system generally comprises a large number of fuel cells, a plurality of bipolar plates each being arranged between neighboring two fuel cells, and a plurality of cooling plates each being arranged every several fuel cells to cool the fuel cells and bipolar plates. In such a fuel cell system, a stacking accuracy of the fuel cell components has a great influence on the performance and sealing properties of the fuel cell system, so that it is required to stack the fuel cell components with high accuracy. However, with increasing the output power of the fuel cell system, the number of fuel cells increases and becomes more than 300, thus making it difficult to assemble the fuel cell stack with a high accuracy.
Heretofore, the fuel cell stack has been assembled, for example, using a simple jig as shown in FIG. 6 which comprises a base 7 and a few props 8 mounted vertically on the base 7, in such a manner that a plurality of fuel cells 2 and bipolar plates 3 are alternately placed one on top of the other so that they are in contact with the props 8 at their adjacent two edges to determine their position, and then tied up with tie bars and tie rods to complete a fuel cell stack 1 and to apply a predetermined compressive load to the fuel cell components to form a seal among them.
However, this method can not be applied to assembly of a fuel cell stack comprising hundreds of fuel cells for the following reasons.
1. The increase in the number of fuel cells causes a great inclination of a fuel cell stack because of an error in thickness of the fuel cell components such as the bipolar plates and cooling plates, thus making it difficult to hold the fuel cell components in the horizontal positions.
2. At the greater the height of the stack, a force acting on the lower components becomes larger than that acting on the upper components, thus making it difficult to apply a uniform force to every fuel cell, resulting in lowering in the characteristics of the fuel cell system.
3. The greater the number of fuel cells stacked, the greater is the height of the stack. Thus, the workers are obliged to engage in a dangerous work high above the ground, resulting in lowering in working efficiency and the safety in work operations.
4. Also, at the greater the height of the fuel cell stack, it is difficult to tie up the fuel cell stack to apply a predetermined compressive load to the fuel cell components. Also, if the fuel cell stack become higher, it is difficult to conduct the attachment of manifolds to the fuel stack. In addition, it is impossible to examine the assemblage of the stack to see if it is suitable or not during the working process.
It is therefore an object of the present invention to provide a method for assembling a fuel cell stack with a high accuracy and with safety in work operations.
Another object of the present invention is to provide a device for assembling a fuel cell stack.
According to the present invention, there is provided a method for assembling a fuel cell stack comprising the steps of alternately stacking the prescribed number of fuel cells and bipolar plates to form a plurality of substacks, arranging the laid substacks on a supporting base so that the central axes of the substacks parallel to the stacking direction of the fuel cell stack are on a horizontal straight line to form a complete fuel cell stack, tying up the fuel cell stack to apply a predeterm1ned compressive load to the fuel cell components, making the fuel cell stack vertical, and then removing said supporting base from the fuel cell stack.
According to the present invention, this method can be carried out with a device for assembling a fuel cell stack that comprises a V-shaped supporting base on which a plurality of fuel cell substacks are arranged, a pair of side plates fixed to both ends of the base, a pressure plate slidably arranged on the base, and means for driving said pressure plate in the transverse direction parallel to the stacking direction of the fuel cell stack.